Light pipes are primarily used for lighting in two main modes. In an end-light mode, the light pipe is optimized to carry light along its length, and transmit it to the output face of the light pipe, typically to a lighting fixture. In a side-light mode, light is extracted from the side of the light pipe and provides illumination along its length. The present invention relates to a side-light mode in which light is extracted in an efficient, and preferably uniform, manner from the side of a light pipe. The portion of a light pipe in which light is extracted from the side of the light pipe is referred to herein as a “luminaire.” Luminaires can be integrated with end-light mode light pipe systems or luminaires can be directly coupled to a source.
One known luminaire is disclosed in U.S. Pat. No. 5,857,761 to Abe et al. The Abe et al. patent is directed to the specialized application of providing light to a thin, flat display panel such as used as a display for notebook computers. Abe et al. had a lesser need for efficiency and directionality of light extraction from a luminaire as compared to applications for lighting wide areas, as, for instance, a person's office. Abe et al., in fact, employs diffusion members in some embodiments to achieve uniformity at the expense of efficiency and directionality since their luminaire does not achieve on its own adequate uniformity.
U.S. Pat. No. 6,488,397 to Masutani et al. discloses a luminaire with a constant-width strip of light-extraction means. However, the Masutani et al. disclosure does not address the concerns of efficiency and uniformity of illumination addressed by the various embodiments of the present invention.
US Patent Publication No. 20020159741A1 discloses various applications of luminaires. However, such applications do not address the efficiency and uniformity of illumination addressed by the various embodiments of the present invention.
In connection with an embodiment of the invention including a reflecting enclosure spaced from a luminaire, U.S. Pat. No. 6,095,673 to Goto et al. discloses a luminaire with an enclosure. However, the enclosure of Goto et al. intimately contacts the luminaire so that there is no air gap between luminaire and enclosure.
It would be, thus, desirable to provide luminaires having embodiments providing efficiency of illumination, and preferably also uniformity of illumination arranged, while accommodating the angular distribution of light from different light sources.
The present invention provides, in a preferred form, a luminaire with directional side-light extraction. The luminaire comprises a light pipe with a light-carrying core. The light-pipe has a first end in which light from a first light source is received, a second end, and a longitudinal axis. The surface of the core of the light pipe has a light-extraction means along a first longitudinal side of the luminaire, which is confined to a radial swath of the luminaire, along the longitudinal axis of the luminaire, of substantially less than 180°. The second end of the light pipe has light-savings means for directing saved light from the second end towards the first end.
In one embodiment, the light-extraction means is adjustable to accommodate angular distributions of light from each one of the light sources of a metal halide lamp, an LED lamp or a halogen lamp, one at a time.
In another embodiment, the light-extraction means is adjustable to accommodate angular distributions of light from a high illuminance light source with luminance greater than 100,000 Nit.
In yet another embodiment, the light-extraction means is adjustable to accommodate angular distributions of light from an array of LED lamps, which lamps may have different colors.
The foregoing inventive luminaires achieve a high efficiency, largely due to inclusion of light-saving means at the second end of the luminaire. Various embodiments of the invention also achieve a high degree of uniformity of illumination. This is true, although the inclusion of the light-saving means often requires a more careful patterning of the light-extraction means to achieve uniformity.
Other features and advantages of the invention will become apparent from the following specification in connection with the appended drawings.